Apparatus for injecting medicinal solutions



July 18, 1950 D. PRYTz APPARATUS Foa INJECTING MEDICINAL soLu'rIoNs Filed Nov. 25, 1947 lNvENTOR ,Den P/yzz ATTORNEYS Patented July 18, 1950 APPARATUS FOR INJECTING MEDICINAL SOLUTIONS Dan Prytz,` Svendborg,` Denmark Application November 25, 1947, Serial No. 787,929 In Denmark November 26, 1946 (Cl. 12S-232) 2 Claims. 1

This invention relates to an apparatus which is suitable for use in continuously injecting medicinal solutions into a patient at a slow, substantially constant rate.

In continuous injection (i. e., the infusion into a patient of liquids containing medicinals such as penicillin), a constant and slow rate of injection is as a rule desired so that only a small volume of liquid is injected per unit or time. Slow speed of injection is achieved by decreasing the speed of flow of the liquid from the injection apparatus. This is usually achieved by narrowing the bore of the tube through which the liquid ows, by means of a screw clamp. Since the bore of the tube through which the liquid flows is narrowed down to a Very high degree, impurities in the liquid easily clog the tube. As a result, frequent control and adjustment of the speed of flow is necessary in order to insure a fairly constant rate of injection.

It is therefore an object of the present invention to provide an apparatus for injecting medicinal solutions, from which apparatus the liquid will flow substantially freely through the outlet tube.

It is also an object of the presen-t invention to provide an apparatus for injecting medicinal solutions which need be adjusted at less frequent intervals.

The aforementioned and other objects are accomplished in accordance with the present invention by providing an apparatus having a reservoir adapted to hold a suply of the medicina1 solution, which reservoir has in communication therewith an outlet line for the solution and also in communication therewith an air inlet line having therein a capillary tube.

For a more complete understanding of the apparatus of the present invention, reference is made to the accompanying drawing which illustrates in diagrammatic form the invention in a preferred embodiment. The apparatus of the drawing shows a container or reservoir I for the bulk of the liquid to be injected, having a exible connection tube 2 and an exit tube 3 through which the liquid may flow with the aid of gravity to the body of the patient. The exit tube 3 is shaped in the form of a hypodermic needle such as is usually used by physicians. On the connection tube 2 there is placed a screw clamp 4, the function of which will be explained hereinafter, The container I is also supplied with a flexible filling tube 5 which is closed by a screw clamp 6 when the apparatus is being used. The tubes numbered I2, 9, l, I0 and 8 together make up the air intake or air inlet of the apparatus. Before 2 the atmospheric air enters the capillary tube .'I, it is purified by passing through the filter 8,- a tube which may for example contain cotton as a ltering material. The container may be supplied with additional supply tubes 5 and/or with additional exit tubes 2 and 3 not shown on the drawing.

The apparatus just described operates essentially in the following fashion. The liquid in the container I ilows by means of gravity through the connection tube 2 and through the exit tube 3 to the-body of the patient. When equilibrium has been reached, the air in the container I is at a pressure` less than atmospheric and the volume rate at which the liquid flows from the container l will equal the volume rate at which air is drawn from the atmosphere into the container I through the capillary tube 1. The rate at which the air enters the container I will be substantially constant, and will depend primarily upon the internal diameter of the capillary tube, but also upon the length thereof and upon the difference in air pressure between the two ends of the capillary tube 1. A very ne degree of regulation of the rate of ilow of liquid may be made by a change in the vertical distance between the liquid level in the container I and the exit tube 3. The inuence of the dimensions of the other parts of the apparatus on the rates of the flow of the air and liquid may, for all practical purposes, be disregarded, since all these parts possess a very large diameter in comparison with the diameter of the capillary tube.

In making the apparatus ready for use, liquid is added to the container I through the supply tube 5 while the screw clamp 6 is open and the screw clamp Il is closed tight. Then, when an injection is being made using the apparatus, the supply tube 5 is closed tight by means of the screw clamp 6, and the screw clamp 4 on the connection tube 2 between the container I and the exit tube 3 is held wide open.

The particular dimensions chosen for the apparatus, particularly the diameter and length of the capillary tube, will depend Iupon the rate at which it is desired that liquid will flow from the apparatus. For example, an apparatus having a capillary 0.005 cm. in diameter and 8.67 cm. long will deliver liquid at the rate of about ml. per day, when the vertical distance between the liquid level in the container and the exit tube is 10o cm. When the aforementioned vertical distance is reduced to 50 om., the apparatus will deliver liquid at the rate of about 50 ml. per day. Likewise, when the length of the 0.005 cm. diameter capillary is increased to 17.33 cm. and thel vertical distance is held at 100 cm., the apparatus will deliver liquid at the rate of 50 ml, per day. Furthermore, when a capillary 0.01 cm. in diameter and 8.67 cin. long is used and the vertical distance is held at 100 cm., the apparatus will deliver about 1600 ml. per day. As a general rule, according to Bernoullis law which is Well known in the eld of hydraulics and hydrodynamics, the rate of flow from an apparatus will be proportional to the fourth power of the diameter of the capillary, Will be proportional to the vertical distance between the surface of the liquid in the container and the exit tube, and will be inversely proportional to the length of the capillary tube.

Various modications may be made in the apparatus specifically described. Thus, the ilexible connection tube 9 between the container I and the capillary tube 1 may be closed 01T with a screw clamp (not shown) when the container l is being lled through the supply tube 5. This will prevent the liquid from owing back into the capillary tube l. Alternatively, a lter of non-absorbable cotton or a valve may be inserted in the connection tube 9 for the same purpose. In addition, asmall bubble counter Il may be inserted either before, between, or after the inlet tubes 8, I0, l and 9. The rate at which the ingoing air bubbles through this bubble counter provides a measure of the rate at which the air is entering the apparatus, and consequently of the rate at which the liquid is flowing from the apparatus. Glycerine is a liquid suitable for use in such a bubble counter. Still other modifications may be made by those skilled in the art.

I claim:

l. An apparatus suitable for use in continuously injecting medicinal solutions into a patient at a slow, substantially constant rate comprising a reservoir adapted to hold a supply of the medicinal solution, the reservoir having in communication therewith an outlet line for the solution and an air inlet line having a capillary tube therein, said capillary tube forming thev sole means for regulating the discharge of solution through the outlet line.

2. An apparatus suitable for use in continuously injecting medicinal solutions into a Ipatient at a slow, substantially constant rate comprising a reservoir adapted to hold a supply of the medicinal solution, the reservoir having in communication therewith an outlet line for the Solution and an air inlet line having therein a capillary tubey and air ltering means, said capillary tube being between said filtering means and said reservoir and forming the sole means for regulating the discharge of solution through the outlet line.

DAN PRYTZ'.

REFERENCES CITED The following references are of record in th file of. this patent:

UNITED STATES PATENTS- Number Name Date 43,158 Shepard' June 14, 1864 2,121,123 Erikson et al. June 21, 1938 2,214,260' Ravenscroft et al. Sept. 10, 1940 2,231,418 Trotter Feb. 1l, 1941 2,333,685 Schwab Nov. 9 1943 

